1. Field of the Invention
The present invention relates to digital video recorders. More particularly, the present invention relates to communicating a channel-change event from a set top box to a digital video recorder.
2. Description of the Prior Art
FIG. 1A shows a prior art digital video recorder or DVR 2 installed between a set top box 46 or STB 4 (e.g., a tuner for digital cable) and a monitor 6. The STB 4 demodulates a selected channel from a program signal 5 and provides an audio and video (A/V) signal 7 to the DVR 2. The DVR 2 may record the A/V signal 7 for playback at a later time, or pass the A/V signal 7 through to the monitor 6 as A/V signal 9. The DVR 2 further comprises a modem for receiving Electronic Program Guide (EPG) data over a telephone line 8. The user operates a remote control 10 to direct the DVR 2 to display the EPG data on the monitor 6 in a DVR graphical user interface (GUI). The user can peruse the EPG data in the DVR GUI to select various programs to view and/or record.
The remote control 10 is also used to control the operation of the STB 4; that is, the remote control 10 of the DVR 2 is intended to replace the remote control of the STB 4. Commands are sent from the DVR 2 to the STB 4 over a control line 12. For example, if the user selects a new channel with the remote control 10, the DVR 2 commands the STB 4 to tune to the selected channel. In another example, if a program the user previously selected for recording begins to air, the DVR 2 directs the STB 4 to tune to the appropriate channel.
Although the remote control 10 of the DVR 2 is intended to replace that of the STB 4, the user can still control the operation of the STB 4 using its remote control. In addition, the user may operate the STB 4 (e.g., change the channel) by pressing buttons on the faceplate of the STB 4. Prior art DVRs have no way of knowing if the user has changed the channel by controlling the STB 4 directly which can disrupt the proper operation of the DVR 2.
There is, therefore, a need for a DVR capable of detecting when a user has changed a channel tuned by a STB.